{
 "cells": [
  {
   "cell_type": "markdown",
   "id": "74bd4666",
   "metadata": {},
   "source": [
    "# 函数\n",
    "\n",
    "## 函数的定义\n",
    "> 1.数学 :     f(x) = ax + b\n",
    "> 2.python : def fib(x \n",
    "> 3.编程思维 vs 数学思维\n",
    ">> 1. 斐波那契数列命名\n",
    ">> 2. 函数可以被定义名称\n",
    ">> 3. 数学思维是写在同一行（定义函数 和 运算公式），面向对象编程中 函数写多行，定义函数\n",
    ">> 4. 数学函数一般没有注释，而编程过程中，一般需要对函数进行注释描述（docstring，课本P151）\n",
    ">> 5. 数学中：ax + b 是计算公式 ，而编程中，我们将函数的内容成为**函数体**,函数体要有一定的**缩进**\n",
    ">> 6. 数学函数执行，将参数带入公式 ， 编程中函数执行，将参数带入函数体\n",
    "## 函数的进阶"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "f2c6804b",
   "metadata": {},
   "source": [
    "# 函数的定义\n",
    ">   定义函数\n",
    "\n",
    "def:定义函数的关键字                               \n",
    "flb：函数名                                        \n",
    "(n)：定义函数的参数                             \n",
    "\"\"\"  \"\"\"：文档描述                             \n",
    "代码块：                                                    \n",
    "     a, b = 0, 1                              \n",
    "     while a < n:                                               \n",
    "        print(a, end=' ')                                 \n",
    "         a, b = b, a+b                            \n",
    "     print()                                   "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "id": "73e52143",
   "metadata": {},
   "outputs": [],
   "source": [
    "# 斐波那契数列：0 1 1 2 3 5 8 13 21 34\n",
    "def fib(x):\n",
    "    '''列出确定s以内的斐波那契数列'''\n",
    "    a, b = 0, 1\n",
    "    while(a < x):\n",
    "        print(a,end= \"\")\n",
    "        a, b =b, a+b\n",
    "        "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "id": "ef3a67e9",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "01123581321345589"
     ]
    }
   ],
   "source": [
    "fib(100)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 22,
   "id": "0a3a6846",
   "metadata": {},
   "outputs": [],
   "source": [
    "# 实践：请大家写一个函数，这个函数可以打印 “你好，xx同学”\n",
    "def fib(name):\n",
    "    '''显示问候语'''\n",
    "    print(\"你好，%s同学\"%(name))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 23,
   "id": "bf73fe3d",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "你好，小丁同学\n"
     ]
    }
   ],
   "source": [
    "fib(\"小丁\")"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "7570d2d4",
   "metadata": {},
   "source": [
    "> 2.调用函数/使用函数\n",
    ">> 1.函数名(参数)                                             \n",
    ">> 2.参数可以不存在"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "id": "86bea013",
   "metadata": {},
   "outputs": [],
   "source": [
    "def hello():\n",
    "    \"\"\"显示问候语\"\"\"\n",
    "    print(\"hello,world\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "id": "c236674b",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Help on function hello in module __main__:\n",
      "\n",
      "hello()\n",
      "    显示问候语\n",
      "\n"
     ]
    }
   ],
   "source": [
    "help(hello)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 26,
   "id": "faa38d6e",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "hello,world\n"
     ]
    }
   ],
   "source": [
    "hello()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 27,
   "id": "37f6d370",
   "metadata": {},
   "outputs": [],
   "source": [
    "# 回顾与思考\n",
    "import time"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 28,
   "id": "727138a7",
   "metadata": {},
   "outputs": [],
   "source": [
    "# sleep() 需要给定一个时间（int）参数\n",
    "time.sleep(3)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 29,
   "id": "7f14889f",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "time.struct_time(tm_year=2021, tm_mon=12, tm_mday=2, tm_hour=11, tm_min=22, tm_sec=54, tm_wday=3, tm_yday=336, tm_isdst=0)"
      ]
     },
     "execution_count": 29,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# localtime() 不需要给定参数\n",
    "time.localtime()"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "6acc6e6d",
   "metadata": {},
   "source": [
    "> 3.函数的优势\n",
    ">>  1.可以重复使用相同的功能，避免重复造轮子                 \n",
    ">>  2.使用者可以不了解函数本身，只需要清楚如何使用即可                 \n",
    ">>  3.使用/调用方便，只需要清楚传递的 函数名及参数"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "aad49b02",
   "metadata": {},
   "source": [
    "# 函数的参数\n",
    "> 1. 形式参数（形参）: 形式参数，不是实际存在的，是虚拟变量。在定义函数和函数体的时候使用形参，目的是在函数调用时接收实参\n",
    ">> 1. 在**定义**函数的时候定义的参数\n",
    ">> 2. 形式参数不占用内存\n",
    "> 2. 实际参数（实参）：实际参数，调用函数时传递给函数的参数，可以是常量、变量，表达式，函数，传给形参\n",
    ">> 1. 在**调用**函数的时候传递的参数\n",
    ">> 2. 调用函数时，形式参数分配空间，传递实际参数，执行函数内容"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "4787b55b",
   "metadata": {},
   "source": [
    "* 课本函数实践案例\n",
    "\n",
    "def search4vowels(word):                           \n",
    "    \"\"\"显示文本中出现的元音字母有哪些\"\"\"                                   \n",
    "    vowels = set(\"aeiou\")                        \n",
    "    word = set(word)                                   \n",
    "    print(vowels & word)                              "
   ]
  },
  {
   "cell_type": "markdown",
   "id": "a3f65c77",
   "metadata": {},
   "source": [
    "> 形式参数： word                       \n",
    "> 实际参数：\"fbheduigpewjiewmcfkdlaepw\""
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "id": "9dd6fcc6",
   "metadata": {},
   "outputs": [],
   "source": [
    "#  课本函数实践案例\n",
    "def search4vowels(word):\n",
    "    \"\"\"显示文本中出现的元音字母有哪些\"\"\"\n",
    "    vowels = set(\"aeiou\")\n",
    "    word = set(word)\n",
    "    print(vowels & word)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "id": "4d00ff19",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Help on function search4vowels in module __main__:\n",
      "\n",
      "search4vowels(word)\n",
      "    显示文本中出现的元音字母有哪些\n",
      "\n"
     ]
    }
   ],
   "source": [
    "help(search4vowels)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 33,
   "id": "fd930323",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "{'a', 'u', 'e', 'i'}\n"
     ]
    }
   ],
   "source": [
    "search4vowels(\"fbheduigpewjiewmcfkdlaepw\")"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "957a0097",
   "metadata": {},
   "source": [
    "* 在多个参数的情境下\n",
    "\n",
    "> 1. 位置参数(positional argument)\n",
    ">> 1. 在形式参数的定义中，有一定的先后顺序                      \n",
    ">> 2. 在调用函数时，要考虑形参的先后顺序                      \n",
    ">> 3. 调用函数时，不仅要考虑参数位置，还需要考虑形式参数的个数\n",
    "> 2. 关键数参数\n",
    ">> 在调用函数时，关键字参数可以不考虑形式参数的位置\n",
    "> 3. 默认参数\n",
    ">> 1.调用函数时，可以省略传递的参数信息                                      \n",
    ">> 2.调用函数时，如果给默认参数赋值，会替换默认参数的结果"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "id": "254f4448",
   "metadata": {},
   "outputs": [],
   "source": [
    "def describe_pet(pet_name,animal_type):\n",
    "    \"\"\"显示宠物信息\"\"\"\n",
    "    print(\"\\nI have a \" + animal_type + \".\")\n",
    "    print(\"My \" + animal_type + \"'s name is \"+pet_name.title() + \".\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "id": "a871550f",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "\n",
      "I have a dog.\n",
      "My dog's name is 豆豆.\n"
     ]
    }
   ],
   "source": [
    "describe_pet(\"豆豆\",\"dog\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "id": "2d65fc3f",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "\n",
      "I have a 豆豆.\n",
      "My 豆豆's name is Dog.\n"
     ]
    }
   ],
   "source": [
    "describe_pet(\"dog\",\"豆豆\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "id": "1dca132e",
   "metadata": {},
   "outputs": [
    {
     "ename": "TypeError",
     "evalue": "describe_pet() missing 1 required positional argument: 'animal_type'",
     "output_type": "error",
     "traceback": [
      "\u001b[1;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[1;31mTypeError\u001b[0m                                 Traceback (most recent call last)",
      "\u001b[1;32m<ipython-input-11-7b9959e7e395>\u001b[0m in \u001b[0;36m<module>\u001b[1;34m\u001b[0m\n\u001b[1;32m----> 1\u001b[1;33m \u001b[0mdescribe_pet\u001b[0m\u001b[1;33m(\u001b[0m\u001b[1;34m\"豆豆\"\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0m",
      "\u001b[1;31mTypeError\u001b[0m: describe_pet() missing 1 required positional argument: 'animal_type'"
     ]
    }
   ],
   "source": [
    "describe_pet(\"豆豆\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "id": "14e5b255",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "\n",
      "I have a cat.\n",
      "My cat's name is 微积分.\n"
     ]
    }
   ],
   "source": [
    "describe_pet(animal_type=\"cat\",pet_name=\"微积分\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 13,
   "id": "8e99dba4",
   "metadata": {},
   "outputs": [],
   "source": [
    "## 默认参数\n",
    "def describe_pet(pet_name,animal_type=\"dog\"):\n",
    "    \"\"\"显示宠物信息\"\"\"\n",
    "    print(\"\\nI have a \" + animal_type + \".\")\n",
    "    print(\"My \" + animal_type + \"'s name is \"+pet_name.title() + \".\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 14,
   "id": "f3e65a77",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "\n",
      "I have a cat.\n",
      "My cat's name is 豆豆.\n"
     ]
    }
   ],
   "source": [
    "describe_pet(\"豆豆\",\"cat\")"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "82babcd9",
   "metadata": {},
   "source": [
    "*参数注意事项实践\n",
    "> 1.位置参数和关键字参数同时使用（调用函数）                                         \n",
    ">> 1.positional argument follows keyword argument（关键字参数均应该放在位置参数之后）                 \n",
    ">> 2.只要满足1的条件，剩余的关键字参数（多个）不考虑先后顺序 \n",
    "\n",
    "> 2.非默认参数和默认参数同时使用（定义函数）                        \n",
    ">> 1.non-default argument follows default argument（默认参数均应该放在非默认参数之后）                          \n",
    ">> 2.只要满足1的条件，剩余的默认参数（多个）不考虑先后顺序                     "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 18,
   "id": "695fd4e2",
   "metadata": {},
   "outputs": [],
   "source": [
    "def test(x,y,z):\n",
    "    \"\"\"打印x,y,z的结果\"\"\"\n",
    "    print(x)\n",
    "    print(y)\n",
    "    print(z)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 19,
   "id": "05f53503",
   "metadata": {},
   "outputs": [
    {
     "ename": "SyntaxError",
     "evalue": "positional argument follows keyword argument (<ipython-input-19-489fdb94d38c>, line 2)",
     "output_type": "error",
     "traceback": [
      "\u001b[1;36m  File \u001b[1;32m\"<ipython-input-19-489fdb94d38c>\"\u001b[1;36m, line \u001b[1;32m2\u001b[0m\n\u001b[1;33m    test(5,y=3,2)\u001b[0m\n\u001b[1;37m               ^\u001b[0m\n\u001b[1;31mSyntaxError\u001b[0m\u001b[1;31m:\u001b[0m positional argument follows keyword argument\n"
     ]
    }
   ],
   "source": [
    "# 实践1：\n",
    "test(5,y=3,2)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 20,
   "id": "6816a5b1",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "5\n",
      "3\n",
      "2\n"
     ]
    }
   ],
   "source": [
    "# 实践2：\n",
    "test(5,3,z = 2)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 21,
   "id": "86e5a1ba",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "5\n",
      "2\n",
      "3\n"
     ]
    }
   ],
   "source": [
    "# 实践3：\n",
    "test(5,z=3,y=2)\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 22,
   "id": "094f70d9",
   "metadata": {},
   "outputs": [
    {
     "ename": "SyntaxError",
     "evalue": "non-default argument follows default argument (<ipython-input-22-eac1f1ed18cb>, line 2)",
     "output_type": "error",
     "traceback": [
      "\u001b[1;36m  File \u001b[1;32m\"<ipython-input-22-eac1f1ed18cb>\"\u001b[1;36m, line \u001b[1;32m2\u001b[0m\n\u001b[1;33m    def test(x,y=1,z):\u001b[0m\n\u001b[1;37m             ^\u001b[0m\n\u001b[1;31mSyntaxError\u001b[0m\u001b[1;31m:\u001b[0m non-default argument follows default argument\n"
     ]
    }
   ],
   "source": [
    "# 测试2：\n",
    "def test(x,y=1,z):\n",
    "    \"\"\"打印x,y,z的结果\"\"\"\n",
    "    print(x)\n",
    "    print(y)\n",
    "    print(z)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 23,
   "id": "eef5c9e7",
   "metadata": {},
   "outputs": [],
   "source": [
    "def test(x,z,y=1):\n",
    "    \"\"\"打印x,y,z的结果\"\"\"\n",
    "    print(x)\n",
    "    print(y)\n",
    "    print(z)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "a1c4fdda",
   "metadata": {},
   "outputs": [],
   "source": []
  }
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